I've been using Ableton Live 8 64-bit beta, and using JBridge to convert a heap of my 32-bit vsts, including dB-AudioWare's sidechain compressor. However, using this sidechain compressor through JBridge with many instances causes Live to crash whenever I close the project. I then have to wait around 5 minutes before I can open Live again.

Is it a Synthedit plugin? In early version of plugs made with SE crashes would occur if multiple instances are inserted on the same project. The work around was to rename a few copies of the .dll in you plugins folder prior to inserting them.